Just scanned my car, it shows that I have a low battery condition on startup, but it displays I'm running at 13.9 volts. Could this cause startup problems and also is this normal and how would I fix it if it is not?

 

After the car is running the alternator starts doing it's thing giving you the 13.9 volts (shows it's charging the battery). I'd say perhaps your battery is getting weak or you have some bad connections. Yes it can cause problems on start up. The ECM and associated components need proper voltage.

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Rob P
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SLP Dual Cold Air Intake 1 5/8" Headers Semi-Siamesed Runners, IROC
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I am using diacom and it shows that i have a charge of no less than 12.3 volts at all time but for some reason it says i have a low power condition. I assume this is just power to the ecm, Which pins and wires should i check?

 

Is this an SES code you are getting? If so, there is no SES code for a low battery condition on a Thirdgen ECM - just high voltage.

There is a Low Voltage SES condition for the Fuel Pump.

 

No one of the data postions on diacom says "battery status" which only sometimes reads low when i first start the car and another data postion says Voltage which after the car starts is imediatly 13.9-14.1. This is with the diacom program and I forgot to mention its on a 91 305 TBI. Hope this clears up everything.

 

Sounds completely normal and logical. If you have your scan tool running (without the engine running), it will show a lower voltage than if the engine is running. When you are first cranking the enigne, you have one of the heaviest electrical loads running off the battery and will get a lower voltage reading. Once the engine starts, the voltage will increase because the alternator is now providing power.

You don't have any problem.

 

During cranking, voltage can drop as low as 9.5 volts, since the starter is pulling over 200+ amps. This is normal. As long as "at rest", the battery is around 12V (11.5-12.5) and engine running, its 13+

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1987 Trans Am 305
14.88 @ 92.81

 

it usually does it for atleast a min after starting and it only does it when the car is warm

 

thanks everyone for your help. I found the problem the guy before me hard wired the fan with the ecm and had not one but two inline splice connector which left the wire so weak when i was unrappin the tape it busted. anyways thanks for the info